1. Field of the Invention
The present invention relates to systems for harvesting energy from water motion and, more specifically, systems that employ the triboelectric effect to harvest water energy.
2. Description of the Related Art
Ambient water motion, presented in forms of river flows, ocean tides and waves, and even rain drops, contain a gigantic reserve of renewable mechanical energy. Taking advantage of this energy has major significance in grid-level energy generation by large-scale power plants for public utilities in order to relieve our sole reliance on limited fossil fuels. Moreover, it also provides a viable route to fulfilling on-site power demand for long-term operation of self-powered autonomous systems, such as off-grid and stand-alone facilities, or remote sensor networks. Most of previously demonstrated converters for water motions depended on normal electromagnetic generators that were bulky and heavy in order for decent output power and conversion efficiency. Besides, they usually required other essential components, such as an absorber that collected ambient water motions, and a turbine that drove the generator, which further expanded the size of the system and added complicity as well as cost. Moreover, natural water motions, especially waves, can be categorized into a number of forms; and not all of them are suitable for driving a turbine. Therefore, a small-sized, lightweight, cost-effective, and all-in-one approach that can directly interact with water bodies is greatly desirable as a key to solving to the problems above.
Initial efforts with this regard included flexible piezoelectric strips (so-called ‘eels’) that undulated in water flow as driven by vortices shed from an upstream bluff body, and low-dimensional carbon nanostructure, e.g. carbon nanotubes and few-layered graphene, over which voltages were induced when polar liquids flew. In the former design, reciprocating-strained eels posed a major challenge to prolonged operation due to mechanical fatigue especially of electrodes, while the latter was restricted by materials availability and by ion concentrations in waters. Besides, both of them only harnessed constant water currents, leaving other forms of water motions largely intact.
Therefore, there is a need for an efficient system for harvesting energy from wave action.